Magnetic coupling device and communication system

ABSTRACT

According to one embodiment, there is provided a magnetic coupling device including a first coil, a second coil, a third coil, a fourth coil, a first constant-potential node and a second constant-potential node. The second coil is electrically connected with one end of the first coil and wound in a direction opposite to a direction in which the first coil is wound. The third coil faces the first coil. The fourth coil faces the second coil. The first constant-potential node is electrically connected with one end of the third coil. The second constant-potential node is electrically connected with one end of the fourth coil.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2016-168275, filed on Sep. 7, 2013; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a magnetic couplingdevice and a communication system.

BACKGROUND

A magnetic coupling device provided between a transmission circuit and areception circuit magnetically couples the transmission circuit and thereception circuit while electrically insulating the circuits from eachother. In this case, it is desired to appropriately perform signaltransmission from the transmission circuit to the reception circuitthrough the magnetic coupling device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a circuit configuration and a signaltransmitting operation of a communication system including a magneticcoupling device according to an embodiment;

FIG. 2 is a diagram illustrating an implemented configuration of themagnetic coupling device according to the embodiment;

FIG. 3 is a diagram illustrating an operation for CMTI noise by thecommunication system including the magnetic coupling device according tothe embodiment;

FIG. 4 is a diagram illustrating an operation for an external magneticfield by the communication system including the magnetic coupling deviceaccording to the embodiment;

FIG. 5 is a diagram illustrating a circuit configuration and a signaltransmitting operation of a communication system including a magneticcoupling device according to a first modification of the embodiment;

FIG. 6 is a diagram illustrating an operation for an external magneticfield by the communication system including the magnetic coupling deviceaccording to the first, modification of the embodiment;

FIG. 7 is a diagram illustrating a circuit configuration and a signal,transmitting operation of a communication system including a magneticcoupling device according to a second modification of the embodiment;

FIG. 8 is a diagram illustrating an operation for an external magneticfield by the communication system including the magnetic coupling deviceaccording to the second modification of the embodiment;

FIG. 9 is a diagram illustrating a circuit configuration of acommunication system including a magnetic coupling device according to athird modification of the embodiment;

FIGS. 10A, 10B, and 10C are each a diagram illustrating a circuitconfiguration of a constant-potential generation circuit according tothe third modification of the embodiment; and

FIG. 11 is a diagram illustrating a circuit configuration of acommunication system including a magnetic coupling device according to afourth modification of the embodiment and an operation for an externalmagnetic field by the communication system.

DETAILED DESCRIPTION

In general, according to one embodiment, there is provided a magneticcoupling device including a first coil, a second coil, a third coil, afourth coil, a first constant-potential node and a secondconstant-potential node. The second coil is electrically connected withone end of the first coil and wound in a direction opposite to adirection in which the first coil is wound. The third coil faces thefirst coil. The fourth coil faces the second coil. The firstconstant-potential node is electrically connected with one end of thethird coil. The second constant-potential node is electrically connectedwith one end of the fourth coil.

Exemplary embodiments of a magnetic coupling device will be explainedbelow in detail with reference to the accompanying drawings. The presentinvention is not limited to the following embodiments.

Embodiment

The following describes a magnetic coupling device according to anembodiment. The magnetic coupling device is used to perform signaltransmission while electrically insulating a primary side circuit and asecondary side circuit from each other, for example, when operationvoltage is largely different between the primary side circuit and thesecondary side circuit. In a communication system including the magneticcoupling device, the primary side circuit includes a transmissioncircuit, and the secondary side circuit includes a reception circuit.The magnetic coupling device is disposed between the transmissioncircuit and the reception circuit so that a coil corresponding to thetransmission circuit and a coil corresponding to the reception circuitcan be electrically insulated from each other and magnetically coupledwith each other. In this case, the magnetic coupling device is desiredto appropriately transmit the signal from the coil on the transmittingside (primary side) to the coil on the receiving side (secondary side)while maintaining the insulation between the transmission circuit andthe reception circuit. The magnetic coupling device is also desired tobe applicable to a system in which the voltage difference between powervoltages connected with the transmission circuit and the receptioncircuit is large and the operation speed of an element (for example, SiCor GaW) of an electronic circuit as a load is fast.

In the magnetic coupling device, the coils magnetically coupled witheach other can be electrically insulated from each other by aninsulating film. The magnetic coupling device may employ a doubleinsulation configuration so that the magnetic coupling device can bemounted on an on-board instrument, and/or an industrial instrument forwhich high reliability is requested. The double insulation configurationcan easily secure sufficient dielectric voltage between the primary sidecoil and the secondary side coil, thereby satisfying thehigh-reliability request. In addition, the configuration guaranteessecure operation of the function of an on-board instrument or anindustrial instrument on which increasingly higher voltage is applied.However, a single insulation configuration may be employed when thereliability of the dielectric voltage is not so much requested in usagesuch as communication. In the single insulation configuration, a pair ofcoils on the primary or secondary side may be removed, and the remainingpair of coils may be directly connected with the transmission circuit orthe reception circuit. Effects as described later are provided for thecircuit connected with the pair of coils.

However, in the magnetic coupling device, the primary side coil and thesecondary side coil are electrically insulated from each other, and asignal to be transmitted is a high-frequency signal. Thus, in themagnetic coupling device, electromagnetic interference (EMI) noise ispotentially emitted to the outside when a high-frequency signal istransmitted between the primary side coil and the secondary side coil.It is desired to not only transmit a signal from the primary side coilto the secondary side coil but also reduce the EMI noise.

Since the magnetic coupling device includes the primary side coil, thesecondary side coil, and resulting parasitic capacitances, noise currentflows to the primary side through a parasitic capacitance, for example,when in-phase noise is generated on the secondary side, and then theprimary side is potentially affected by common mode transient immunity(CMTI) noise. The CMTI is a specification required for the magneticcoupling device, and indicates that no false operation occurs when astepped waveform with an abrupt gradient or the like is input to theprimary side and the secondary side with the magnetic coupling device inoperation. Reduction of the CMTI noise is desired to appropriatelytransmit only a signal from the primary side coil to the secondary sidecoil. The CMTI noise is desired to be further reduced as compared with acase in which the CMTI noise is reduced mainly through a single path.

Thus, in the embodiment, the magnetic coupling device has a doubleinsulation configuration including two sets of an 8-shaped ormeander-shaped coil and two coils facing the 8-shaped or meander-shapedcoil, each of the two coils being connected with a constant-potentialnode. This configuration provides safe operation of the function of themagnetic coupling device, reduction of the EMI noise and the CMTI noise,and a high noise-resistance amount with a minimum number of components.

Specifically, a communication system 1 including a magnetic couplingdevice 30 may have a configuration as illustrated in FIG. 1. FIG. 1 is adiagram illustrating the configuration of the communication system 1including the magnetic coupling device 30.

The magnetic coupling device 30 has a differential configuration. Themagnetic coupling device 30 converts a pair of differential signalstransferred from a primary side circuit 10 into magnetic field energy,converts the magnetic field energy into a pair of differential signalsagain, and transfers the converted differential signals to a secondaryside circuit 20.

The primary side circuit 10 includes an electronic circuit 11 and atransmission circuit 40. The secondary side circuit 20 includes areception circuit 50 and an electronic circuit 21. The transmissioncircuit 40 and the reception circuit 50 may each have a differentialconfiguration.

The transmission circuit 40 is disposed between the electronic circuit11 and the magnetic coupling device 30. The transmission circuit 40includes a differential driver circuit 41. The differential drivercircuit 41 is a differential amplifier of a single-phase input anddifferential output type, and has an input terminal 41 a electricallyconnected with an output node 11 a of the electronic circuit 11, anon-inverting output terminal 41 b electrically connected with a P-sideinput node 30 ip of the magnetic coupling device 30, and an invertingoutput terminal 41 c electrically connected with an N-side input node 30in of the magnetic coupling device 30.

The electronic circuit 11 may have a differential configuration. In thiscase, the differential driver circuit 41 may be a differential amplifierof a differential input and differential output type. The differentialdriver circuit 41 has a non-inverting input terminal electricallyconnected with a non-inverting output node of the electronic circuit 11,and an inverting input terminal electrically connected with an invertingoutput node of the electronic circuit 11.

The reception circuit 50 is disposed between the magnetic couplingdevice 30 and the electronic circuit 21. The reception circuit 50includes a differential receiver circuit 51, The differential receivercircuit 51 is a differential amplifier of a differential input andsingle-phase output type, and has a non-inverting input terminal 51 aelectrically connected with a P-side output node 30 op of the magneticcoupling device 30, an inverting input terminal 51 b electricallyconnected with an N-side output node 30 on of the magnetic couplingdevice 30, and an output terminal 51 c electrically connected with aninput node 21 a of the electronic circuit 21.

The electronic circuit 21 may have a differential configuration. In thiscase, the differential receiver circuit 51 may be a differentialamplifier of a differential input and differential output type. Thedifferential receiver circuit 51 may have a non-inverting outputterminal electrically connected with a P-side input node of theelectronic circuit 21, and an inverting output terminal electricallyconnected with an N-side input node of the electronic circuit 21.

The magnetic coupling device 30 may have a double insulationconfiguration. The magnetic coupling device 30 includes a coil (firstcoil) 31, a coil (second coil) 32, a coil (third coil) 33, a coil(fourth coil) 34, a coil (fifth coil) 35, a coil (sixth coil) 36, a coil(seventh coil) 37, a coil (eighth coil) 38, a capacitor element (firstcapacitor element) C, a capacitor element (second capacitor element) C2,a capacitor element (third capacitor element) C3, a capacitor element(fourth capacitor element) C4, a node (first constant-potential node)N1, a node (second constant-potential node) N2, a node (thirdconstant-potential node) N3, a node (fourth constant-potential node) N4,a bonding wire W1, and a bonding wire W2.

The primary side circuit 10 and some components (namely, the coil 31,the coil 32, the coil 33, the coil 34, the capacitor element C1, thecapacitor element C2, the node N1, and the node N2) of the magneticcoupling device 30 are included in a chip region 102 corresponding to asubstrate 2 (refer to FIG. 2). The secondary side circuit 20 and theother components (namely, the coil 35, the coil 36, the coil 37, thecoil 38, the capacitor element C3, the capacitor element C4, the nodeN3, and the node N4) of the magnetic coupling device 30 are included ina chip region 105 corresponding to a substrate 5 (refer to FIG. 2).

The coil 31 and the coil 32 form an 8-shaped or meander-shaped coil. Thecoil 31 has one end electrically connected with the coil 32, and theother end electrically connected with the coil 35 through the bondingwire W1. The coil 32 has one end electrically connected with the coil31, and the other end electrically connected with the coil 36 throughthe bonding wire W2. The coil 31 and the coil 32 are wound in directionsopposite to each other.

The coil 33 is disposed below the coil 31, facing the coil 31 through aninsulating film (refer to FIG. 2). With this configuration, the coils 31and 33 are electrically insulated from each other and magneticallycoupled to form a transformer. The coil 33 has one end electricallyconnected with the node N1, and the other end electrically connectedwith one end of the capacitor element C1. The node N1 is electricallyconnected with a constant potential, for example, a power potentialVDD1. The power potential VDD1 may be a potential supplied from theoutside of the chip region 102.

The capacitor element C1 has one end electrically connected with thecoil 33, and the other end electrically connected with the non-invertingoutput terminal 41 b of the differential driver circuit 41. Thecapacitor element C1 functions as a coupling capacitor configured totransfer a P-side signal in a differential signal output from thedifferential driver circuit 41 to the coil 33 side (after converting thesignal into voltage, electric field, and then current), therebygenerating current indicated by a dashed-line arrow.

The coil 34 is disposed below the coil 32, facing the coil 32 through aninsulating film (refer to FIG. 2). With this configuration, the coils 32and 34 are electrically insulated from each other and magneticallycoupled to form a transformer. The coil 34 has one end electricallyconnected with the node N2, and the other end electrically connectedwith one end of the capacitor element C2. The node N2 is electricallyconnected with a constant potential, for example, a ground potentialGND1. The ground potential GND1 may be a potential supplied from theoutside of the chip region 102. The coil 33 and the coil 34 areseparated from each other, and the nodes N and N2 are separated fromeach other and may have a plurality of connection points.

The capacitor element C2 has one end electrically connected with thecoil 34 and, the other end electrically connected with the invertingoutput terminal 41 c of the differential driver circuit 41. Thecapacitor element C2 functions as a coupling capacitor configured totransfer an N-side signal in a differential signal output from thedifferential driver circuit 41 to the coil 34 side (after converting thesignal into voltage, electric field, and then current), therebygenerating current indicated by a dashed-line arrow.

Similarly, the coils 35 and 36 form an 8-shaped or meander-shaped coil.The coil 35 has one end electrically connected with the coil 36, and theother end electrically connected with the coil 31 through the bondingwire W1. The coil 36 has one end electrically connected with the coil35, and the other end electrically connected with the coil 32 throughthe bonding wire W2. The coil 35 and the coil 36 are wound in directionsopposite to each other.

The coil 37 is disposed below the coil 35, facing the coil 35 through aninsulating film (refer to FIG. 2). With this configuration, the coils 35and 37 are electrically insulated from each other and magneticallycoupled to form a transformer. The coil 37 has one end electricallyconnected with the node N3, and the other end electrically connectedwith one end of the capacitor element C3. The node N3 is electricallyconnected with a constant potential, for example, a power potentialVDD2. The power potential VDD2 may be a potential supplied from theoutside of the chip region 105.

The capacitor element C3 has one end electrically connected with thecoil 37, and the other end electrically connected with the non-invertinginput terminal 51 a of the differential receiver circuit 51. Thecapacitor element C3 functions as a coupling capacitor configured totransfer a P-side signal in a differential signal output from the coil37 to the differential receiver circuit 51 side (after converting intovoltage, electric field, and then voltage), thereby generating currentindicated by a dashed-line arrow.

The coil 38 is disposed below the coil 36, facing the coil 36 through aninsulating film (refer to FIG. 2). With this configuration, the coils 36and 38 are electrically insulated from each other and magneticallycoupled to form a transformer. The coil 38 has one end electricallyconnected with the node N4, and the other end electrically connectedwith one end of the capacitor element C4. The node N4 is electricallyconnected with a constant potential, for example, a ground potentialGND2. The ground potential GND2 may be a potential supplied from theoutside of the chip region 105. The coil 37 and the coil 38 areseparated from each other, and the nodes N3 and N4 are separated fromeach other and may have a plurality of connection points.

The capacitor element C4 is disposed between the coil 38 and thereception circuit 50. The capacitor element C4 has one end electricallyconnected with the coil 38, and the other end electrically connectedwith the inverting input terminal 51 b of the differential receivercircuit 51, The capacitor element C4 functions as a coupling capacitorconfigured to transfer an N-side signal in a differential signal outputfrom the coil 38 to the differential receiver circuit 51 side (afterconverting into voltage, electric field, and then voltage), therebygenerating current indicated by a dashed-line arrow.

The double insulation configuration of the magnetic coupling device 30may be implemented, for example, as illustrated in FIG. 2. FIG. 2 is adiagram illustrating an implemented configuration of the magneticcoupling device 30. In FIG. 2, a Z direction is defined to be adirection perpendicular to the surface of the substrate 2, and an Xdirection and a Y direction are defined to be two directions orthogonalto each other in a plane perpendicular to the Z direction.

For example, the coil 33 may be formed as a coil pattern 33 a includedin a wiring layer 3. The wiring layer 3 is disposed in the +Z directionrelative to the substrate 2 and extends in the X and Y directions. Thecoil pattern 33 a extends along a plane corresponding to the wiringlayer 3. The node N1 electrically connected with the coil 33 is disposedas an electrode pad 2 a on the substrate 2. The coil 34 may be formed asa coil pattern 34 a included in the wiring layer 3. The coil pattern 34a extends along a plane corresponding to the wiring layer 3. The node N2electrically connected with the coil 34 is disposed as an electrode pad2 b on the substrate 2. The coil 31 is disposed at a position facing thecoil 33, and may be formed as a coil pattern 31 a included in a wiringlayer 4. The wiring layer 4 is disposed in the +Z direction relative tothe wiring layer 3, and extends in the X and Y directions. The coilpattern 31 a extends along a plane corresponding to the wiring layer 4.The coil 32 is disposed at a position facing the coil 34, and may beformed as a coil pattern 32 a included in the wiring layer 4. The coilpattern 32 a extends along a plane corresponding to the wiring layer 4.A line pattern 31 b extends between the coil pattern 31 a and the coilpattern 32 a in the wiring layer 4, and electrically connects the coilpattern 31 a and the coil pattern 32 a.

Similarly, the coil 37 may be formed as a coil pattern 37 a included ina wiring layer 6. The wiring layer 6 is disposed in the +Z directionrelative to the substrate 5 and extends in the X and Y directions. Thecoil pattern 37 a extends along a plane corresponding to the wiringlayer 6. The node N3 electrically connected with the coil 37 is disposedas an electrode pad 5 a on the substrate 5. The coil 38 may be formed asa coil pattern 36 a included in the wiring layer 6. The coil pattern 38a extends along a plane corresponding to the wiring layer 6. The node N4electrically connected with the coil 38 is disposed as an electrode pad5 b on the substrate 5. The coil 35 is disposed at a position facing thecoil 37 and may be formed as a coil pattern 35 a included in a wiringlayer 7. The wiring layer 7 is disposed in the +Z direction relative tothe wiring layer 6 and extends in the X and Y directions. The coilpattern 35 a extends along a plane corresponding to the wiring layer 7.The coil 36 is disposed at a position facing the coil 38 and may beformed as a coil pattern 36 a included in the wiring layer 7. The coilpattern 36 a extends along a plane corresponding to the wiring layer 7.A line pattern 35 b extends between the coil pattern 35 a and the coilpattern 36 a in the wiring layer 7, and electrically connects the coilpattern 35 a and the coil pattern 36 a.

In FIG. 2, a region including the substrate 2, the wiring layer 3, andthe wiring layer A corresponds to the chip region 102, and a regionincluding the substrate 5 the wiring layer 6, and the wiring layer 7corresponds to the chip region 105. The bonding wires W1 and W2 aredisposed across the chip region 102 and the chip region 105 The bondingwire W1 has one end connected with electrode 31 a 1 in the coil pattern31 a, and the other end connected with an electrode 35 a 1 in the coilpattern 35 a. The bonding wire W2 has one end connected with anelectrode 32 a 1 in the coil pattern 32 a, and the other end connectedwith an electrode 36 a 1 in the coil pattern 36 a. The bonding wires W1and W2 may be formed of material containing metal (for example, Au) as aprimary component. The bonding wires W1 and W2 have diameters of 30 □mapproximately, for example.

With the double insulation configuration, the magnetic coupling device30 can easily secure sufficient dielectric voltage between the coils 33and 37, and sufficient dielectric voltage between the coils 34 and 38.For example, the dielectric voltage between the coils 33 and 31 can besecured by providing an insulating film between the wiring layer 3 andthe wiring layer 4 in the Z direction, and the dielectric voltagebetween the coils 35 and 37 can be secured by providing an insulatingfilm between the wiring layer 7 and the wiring layer 6 in the Zdirection. Each insulating film may be formed of material containingoxide (for example, silicon oxide) as a primary component, or may beformed of material containing insulating resin (for example, polyimide)as a primary component.

Similarly, sufficient dielectric voltage between the coils 34 and 32 canbe secured by providing an insulating film between the wiring layer 3and the wiring layer 4 in the Z direction, and sufficient dielectricvoltage between the coils 36 and 38 can be secured by providing aninsulating film between the wiring layer 7 and the wiring layer 6 in theZ direction. Each insulating film may be formed of material containingoxide (for example, silicon oxide) as a primary component, or may beformed of material containing insulating resin (for example, polyimide)as a primary component.

The following describes a signal transmitting operation with referenceto FIG. 1. A transformer (for example, the pair of coils 31 and 33, thepair of coils 32 and 34, the pair of coils 35 and 37, or the pair ofcoils 36 and 38) cannot transmit a DC signal (signal having no frequencycomponent in effect) but transmits a modulated signal (signal having afrequency component). In FIG. 1, a signal V_(IN) input from theelectronic circuit 11 to the differential driver circuit 41 is amodulated signal, for example, a signal modulated by an edge triggerscheme or an on-off keying scheme. The format of the signal transmissionmay be in an FSK scheme as well as an ASK scheme. ASK stands foramplitude shift keying and represents amplitude shift modulation. TheASK scheme is a modulation scheme in which digital signal information isrepresented by the amplitude of carrier wave. In a kind of the ASKscheme, referred to as on-off keying (OOK), the ASK modulation ratio isinfinite, and digital signal information is represented by the existenceof the amplitude. FSK stands for frequency shift keying and representsfrequency shift modulation. The FSK scheme is a modulation scheme inwhich digital signal information is represented by the frequency ofcarrier wave.

The signal V_(IN) is a signal (signal having a frequency component)obtained by shifting the original signal to a high frequency band. Thedifferential driver circuit 41 generates differential signals (a P-sidesignal DP and an N-side signal DN) in accordance with the input signalV_(IN), and transfers the signal DP to the coil 33 side through thecapacitor element C1, and the signal DN to the coil 34 side through thecapacitor element C2. Accordingly, as indicated by a dashed-line arrow,the differential driver circuit 41 applies currents in directionsopposite to each other to the coils 33 and 34. The coil 33 and the coil34, which are wound in the same direction, generate magnetic fields (H₁)in directions opposite to each other as illustrated with a solid-linewhite arrow. When the coils 33 and 34 have substantially identicalshapes (for example, have substantially equal diameters and are woundsubstantially equal numbers of times), the magnitudes of the generatedmagnetic fields are substantially equal to each other. However, sincethe coils 31 and 32 are wound in directions opposite to each other,induced voltages thereof due to H₁ are summed.

In this case, in a signal transmitting operation in a configurationincluding the pair of coils 31 and 33 and the pair of coils 32 and 34, amagnetic flux loop illustrated with solid-line white arrows anddashed-line white arrows can be formed, thereby easily reducingexternally emitted magnetic field and thus reducing the EMI noise.

The coils 31 and 35 are connected with each other through the bondingwire W1, and the coils 32 and 36 are connected with each other throughthe bonding wire W2. Accordingly, the sum of induced voltages generatedby the coils 31 and 32 is applied to the coils 35 and 36. The coils 35and 36, which are wound in directions opposite to each other, generatemagnetic fields (H₂) in directions opposite to each other as illustratedwith solid-line white arrows. When the coils 35 and 36 havesubstantially identical shapes (for example, have substantially equaldiameters and are wound substantially equal numbers of times), themagnitudes of the generated magnetic fields are substantially equal toeach other. However, the coils 37 and 38 are wound in directionsidentical to each other. Since the magnetic fields (H₂) havingdirections opposite to each other and magnitudes substantially equal toeach other are applied to the coils 37 and the coil 38, induced voltageshaving magnitudes substantially equal to each other and directionsopposite to each other are generated at the coils. Accordingly, inducedcurrents indicated by dashed-line arrows flow as the signals DP and DNthrough the coils 37 and the coil 38, respectively. The signal DP istransferred to the differential receiver circuit 51 side through thecapacitor element C3, and the signal DN is transferred to thedifferential receiver circuit 51 side through the capacitor element C4.Accordingly, the differential receiver circuit 51 receives the currentsin directions opposite to each other as the signals DP and DN from thecoils 37 and 38 as indicated by dashed-line arrows. The differentialreceiver circuit 51 generates a difference signal V_(OUT) in accordancewith the signals DP and DN and outputs the difference signal V_(OUT) tothe electronic circuit 21. In this manner, modulated signal transmissionis performed.

In this case, in a signal transmitting operation in a configurationincluding the pair of coils 35 and 37 and the pair of coils 36 and 38, amagnetic flux loop illustrated with solid-line white arrows anddashed-line white arrows can be formed, thereby easily reducingexternally emitted magnetic field and thus reducing the EMI noise.

The following describes an operation for the CMTI noise with referenceto FIG. 3. FIG. 3 is a diagram illustrating an operation for the CMTInoise by the communication system 1 including the magnetic couplingdevice 30. The magnetic coupling device 30 has a CMTI resistance amountas one of its properties. Specifically, the CMTI resistance amountindicates whether a false operation occurs in signal transmission whenone of potentials changes with reference to the other potential. In atypical example of the CMTI resistance amount, it is desirable to haveresistance up to the change amount of 100 kV/μs or more when a referencepotential (for example, a power potential and/or a ground potential)changes by 1000 V between the chip region 102 corresponding to thesubstrate 2 and the chip region 105 corresponding to the substrate 5.FIG. 3 illustrates a case in which the reference potential of the chipregion 105 changes with reference to the reference potential of the chipregion 102 in the present embodiment. The pair of coils 33 and 31 andthe pair of coils 34 and 32 face each other through an insulating filmin the chip region 102. Similarly, the pair of coils 37 and 35 and thepair of coils 38 and 36 face each ether through an insulating film inthe chip region 105. Accordingly, parasitic capacitance C_(ISO13),C_(ISO24), C_(ISO57), or C_(ISO68) exists between the coils in eachpair.

When the reference potential of the chip region 105 is changed with thereference potential of the chip region 102 unchanged, reference voltagechange is divided between the parasitic capacitance C_(ISO13) and theparasitic capacitance C_(ISO57) and between the parasitic capacitanceC_(ISO24) and the parasitic capacitance C_(ISO68). When the parasiticcapacitance C_(ISO13), the parasitic capacitance C_(ISO57), theparasitic capacitance C_(ISO24), and the parasitic capacitance C_(ISO68)are substantially equivalent to each other, the reference potential ofthe chip region 102 and about half of the change of the referencepotential of the chip region 105 are applied to both ends of each of theparasitic capacitance C_(ISO13), the parasitic capacitance C_(ISO57),the parasitic capacitance C_(ISO24), and the parasitic capacitanceC_(ISO68). In this case, to electrically charge and discharge theparasitic capacitance C_(ISO57), a P-side noise component (frequencycomponent) flows to the power potential V_(DD2), the node N3, and thenthe coil 37. When the parasitic capacitance C_(ISO57) has an impedancesmaller than that of the capacitor element C3, the P-side noisecomponent is transferred to the coil 37, the parasitic capacitanceC_(ISO57), the coil 35, the bonding wire W1, the coil 31, the parasiticcapacitance C_(ISO13), and then to the coil 33. Furthermore, since thenode N1 has an impedance smaller than that of the capacitor element C1,the P-side noise component flows to the coil 33, the node N1, and thento the power potential VCD_(DD1). Accordingly, the P-side noisecomponent can be prevented from affecting the differential drivercircuit 41 and the differential receiver circuit. 51, which leads toreduction of the CMTI noise.

Similarly, an N-side noise component (frequency component) flows to theground potential G_(ND2), the node N4, and then the coil 38. When theparasitic capacitance C_(ISO68) has an impedance smaller than that ofthe capacitor element C4, the N-side noise component is transferred tothe coil 38, the parasitic capacitance C_(ISO68), the coil 36, thebonding wire W2, the coil 32, the parasitic capacitance C_(ISO24), andthen to the coil 34. Furthermore, since the node N2 has an impedancesmaller than that of the capacitor element C2, the N-side noisecomponent is transferred to the coil 34, the node N2, and then to theground potential G_(ND1). Accordingly, the N-side noise component can beprevented from affecting the differential driver circuit 41 and thedifferential receiver circuit 51, which leads to reduction of the CMTInoise.

Since the P-side noise component and the N-side noise component aretransferred to the reference potentials (the power potential V_(DD1) andthe ground potential G_(ND1)) different from each other in the chipregion 102, the occurrence of power voltage change due to the noisecomponents can be prevented in the chip region 102, and a false circuitoperation due to the CMTI noise can be prevented.

The following describes an operation for an external magnetic field withreference to FIG. 4. FIG. 4 is a diagram illustrating an operation foran external magnetic field by the communication system 1 including themagnetic coupling device 30.

For example, an external magnetic field H_(NOISE) is applied in adirection from the upper side to the lower side in the sheet of FIG. 4.when the external magnetic field H_(NOISE) is generated from a source ata distance significantly larger than the scale of the coils, theexternal magnetic field H_(NOISE) is applied on the coils 31 to 38 in anidentical direction at magnitudes substantially equal to each other.Since the coils 31 and 32 have interlinkage magnetic flux areasidentical to each other and are wound in directions opposite to eachother, no induced voltage due to the external magnetic field H_(NOISE)is generated in effect. Similarly, no induced voltage due to theexternal magnetic field H_(NOISE) is generated in effect at the coils 35and 36. However, in-phase induced voltages are generated at each of thepair of coils 33 and 34 and the pair of coils 37 and 38. As a result,the differential receiver circuit 51 suffers in-phase noises I_(NOISE),but the in-phase noises can be canceled with each other to have noinfluence on a signal reception operation. In addition, influence on thein-phase induced voltages can be reduced by decreasing the outputimpedance of the differential driver circuit 41, which leads to minorinfluence on the differential driver circuit 41.

As described above, in the embodiment, the magnetic coupling device 30has the double insulation configuration including two sets of an8-shaped or meander-shaped coil (the pair of coils 31 and 32 or the pairof coils 35 and 36) and two coils (the pair of coils 33 and 34 or thepair of coils 37 and 38) facing the 8-shaped or meander-shaped coil. Thetwo coils are connected with the respective nodes N1 and N2 or therespective nodes N3 and N4, each having a constant potential. With thisconfiguration, the EMI noise can be reduced and the CMTI noise can bereduced. Accordingly, the magnetic coupling device 30 has a high CMTIand a high noise-resistance amount, and can transmit a modulated signal(differential signal) and excellently operate under an environment witha high external magnetic field, such as a system with a fast operationspeed of an element (for example, SiC or GaN) of an electronic circuitas a load.

The nodes N1 and N2 may have potentials equal to each other, and thenodes N3 and N4 may have potentials equal to each other.

For example, in the chip region 102, the nodes N1 and N2 may be eachelectrically connected with the power potential V_(DD1). Alternatively,for example, the nodes N1 and N2 may be each electrically connected withthe ground potential G_(ND1). The size of a current loop on a paththrough which differential signal current, flows can be reduced when thenodes N1 and N2 have potentials equal to each other as compared with acase in which the nodes N1 arid N2 have potentials different from eachother. Accordingly, an externally emitted magnetic field due to adifferential signal current loop can be easily prevented in the chipregion 102, which leads to reduction of the EMI noise.

Similarly, in the chip region 105, the nodes N3 and N4 may be eachelectrically connected with the power potential V_(DD2). Alternatively,for example, the nodes N3 and N4 may be each electrically connected withthe ground potential G_(ND2). The size of a current loop on a paththrough which differential signal current flows can be reduced when thenodes N3 and N4 have potentials equal to each other as compared with acase in which the nodes N3 and N4 have potentials different from eachother. Accordingly, an externally emitted magnetic field due to adifferential signal current loop can be easily prevented in the chipregion 105, which leads to reduction of the EMI noise.

Alternatively, as a first modification of the embodiment, acommunication system li may have a configuration as illustrated in FIG.5. FIG. 5 is a diagram illustrating a circuit configuration and a signaltransmitting operation of the communication system 1 i including amagnetic coupling device 30 i according to the first modification of theembodiment.

The communication system 1 i illustrated in FIG. 5 includes a primaryside circuit 10 i and the magnetic coupling device 301 in place of theprimary side circuit 10 and the magnetic coupling device 30 (refer toFIG. 1). The primary side circuit 10 i includes a transmission circuit40 i in place of the transmission circuit 40 (refer to FIG. 1). Thetransmission circuit 40 i includes an in-phase driver circuit 41 i inplace of the differential driver circuit 41 (refer to FIG. 1). Themagnetic coupling device 30 i includes a coil 33 i and a coil 34 i inplace of the coil 33 and the coil 34 (refer to FIG. 1) . The coils 33 iand 34 i are wound in directions opposite to each other.

The following describes the signal transmitting operation with referenceto FIG. 5. The in-phase driver circuit 41 i generates currents indicatedby dashed-line arrows through the capacitor element Cl and the capacitorelement C2 in accordance with the input signal V_(IN), and passes thein-phase currents to the coils 33 i and 34 i. Since the coils 33 i and34 i are wound in directions opposite to each other, the respectivecoils generate magnetic fields (H₁) in directions opposite to eachother. Thereafter, the sane signal transmitting operation as that in theembodiment can be performed.

The operation for the CMTI noise is the same as the operation in theembodiment illustrated in FIG. 3. Specifically, unlike the embodiment,the coils 33 i and 34 i are wound in directions opposite to each other,but the winding directions of the coils do riot affect formation of theparasitic capacitances C_(ISO13) and C_(ISO24). Thus, according to thefirst modification of the embodiment, the CMTI noise can be reducedsimilarly to the embodiment.

The operation for an external magnetic field is as illustrated in FIG.6. FIG. 6 is a diagram illustrating the operation for an externalmagnetic field by the communication system 1 i including the magneticcoupling device 30 i according to the first modification of theembodiment. Specifically, since the coils 33 i and 34 i are wound indirections opposite to each other, differential noise currents I_(NOISE)flow to the in-phase driver circuit 41 i when the external magneticfield H_(NOISE) is applied as illustrated in FIG. 6. Thus, influence onthe in-phase induced voltages can be reduced by decreasing the outputimpedance of the in-phase driver circuit 41 i.

In this manner, in the first modification of the embodiment, too, theEMI noise can be reduced and the CMTI noise can be reduced. Accordingly,the magnetic coupling device 30 i has a high CMTI and a highnoise-resistance amount, and can transmit a modulated signal(differential signal) and excellently operate under an environment witha high external magnetic field.

Alternatively, as a second modification of the embodiment, acommunication system 1 j may have a configuration as illustrated in FIG.7. FIG. 7 is a diagram illustrating a circuit configuration and a signaltransmitting operation of the communication system 1 j including amagnetic coupling device 30 j according to the second modification ofthe embodiment.

The communication system 1 j illustrated in FIG. 7 includes a primaryside circuit 10 j and the magnetic coupling device 30 j in place of theprimary side circuit 10 and the magnetic coupling device 30 (refer toFIG. 1). The primary side circuit 10 j includes a transmission circuit40 j in place of the transmission circuit 40 (refer to FIG. 1). Thetransmission circuit 40 j includes a single-phase driver circuit 41 j inplace of the differential driver circuit 41 (refer to FIG. 1). Themagnetic coupling device 30 j includes a capacitor element C1 j and acapacitor element. C2 j in place of the capacitor element C1 and thecapacitor element C2 (refer to FIG. 1). The capacitor element C1 j hasone end electrically connected with the coils 33 and the other endelectrically connected with an output terminal 41 d of the single-phasedriver circuit 41 j through a node N5 j. The capacitor element C2 j hasone end electrically connected with the coils 34 and the other endelectrically connected with the output, terminal 41 d of thesingle-phase driver circuit 41 j through the node N5 j.

The signal transmitting operation is the same as the operation in theembodiment illustrated in FIG. 1, and the operation for the CMTI noiseis the same as the operation in the embodiment illustrated in FIG. 3.

The operation for an external magnetic field is as illustrated in FIG.8. FIG. 8 is a diagram illustrating the operation for an externalmagnetic field by the communication system 1 j including the magneticcoupling device 30 j according to the first modification of theembodiment. Specifically, when the external magnetic field H_(NOISE) isapplied as illustrated in FIG. 8, differential noise currents I_(NOISE)flow to the single-phase driver circuit 43 j. However, for example, thenoise currents cancel each other at the node N5 j on the output terminal41 d side of the single-phase driver circuit 41 j, and the single-phasedriver circuit 41 j is not affected.

In this manner, in the second modification of the embodiment, too, theEMI noise can be reduced and the CMTI noise can be reduced. Accordingly,the magnetic coupling device 30 j has a high CMTI and a highnoise-resistance amount, and can transmit a modulated signal(differential signal) and excellently operate under an environment witha high external magnetic field.

Alternatively, as a third modification of the embodiment, acommunication system 1 k may internally generate constant potentials asillustrated in FIG. 9. FIG. 9 is a diagram illustrating a circuitconfiguration of the communication system 1 k including a magneticcoupling device 30 k according to the third modification of theembodiment.

The communication system 1 k illustrated in FIG. 9 includes a magneticcoupling device 30 k in place of the magnetic coupling device 30 (referto FIG. 1). The magnetic coupling device 30 k further includesconstant-potential generation circuits 131 to 134. Theconstant-potential generation circuits 131 to 134 are circuitsconfigured to internally generate constant potentials in the chipregions 102 and 105. Output nodes Nout of the constant-potentialgeneration circuits 131, 132, 133, and 134 are electrically connectedwith the nodes N1, N2, N3, and N4, respectively. Accordingly, the nodesN1, N2, N3, and N4 are supplied with internal constant potentials fromthe constant-potential generation circuits 131, 132, 133, arid 134,respectively.

For example, when the constant potentials supplied to the nodes N1, N2,N3, and N4 are constant potentials outside of the chip regions 102 and105, the constant potentials being different, between the nodes N1 andN2 and between the nodes N3 and N4, each constant potential is suppliedon a path in a large loop including a bonding wire, a lead frame, and aPCB substrate pattern, and thus potentially easily affected by anexternal magnetic field. The influence of the external magnetic fieldcan be reduced by supplying, to the nodes N1, N2, N3, and N4, internalconstant potentials generated from in-chip constant potentials suppliedfrom the constant-potential generation circuits 131 to 134 asillustrated in FIG. 9.

The constant-potential generation circuits 131 to 134 may be configuredas source follower circuits as illustrated in FIGS. 10A, 10B, and 100.FIGS. 10A, 10B, and 10C are diagrams illustrating circuit configurationsof the respective constant-potential generation circuits in the thirdmodification of the embodiment.

For example the constant-potential generation circuits 131 to 134 eachinclude an HMOS transistor NT1 and a resistance element R1 asillustrated in FIG. 10A. The NMOS transistor NT1 has a gate electricallyconnected with an input node Nin, a drain electrically connected with apower source node Nv, and a source electrically connected with an outputnode Nout and one end of the resistance element R1. The resistanceelement R1 has one end electrically connected with the source of theHMOS transistor NT1 and the output node Nout, and the other endelectrically connected with a ground node Ng. The input node Nin may besupplied with, for example, an internal power potential from a regulatorcircuit (not illustrated) in the chip regions 102 and 105. The powersource node Nv may be supplied with a power potential (for example, thepower potential V_(DD1) or the power potential V_(DD2)) from the outsideof the chip regions 102 and 105. The ground node Ng may be supplied witha ground potential (for example, the ground potential G_(ND1) or theground potential G_(ND2)) from the outside of the chip regions 102 and105. To reduce AC output impedance, a capacitor element may be providedto the output node Nout as illustrated with dashed lines. With thesource follower circuit configured as illustrated in FIG. 10A, aconstant potential is output from the output node Nout.

Alternatively, the constant-potential generation circuits 131 to 134each include an NMOS transistor NT2 and an NMOS transistor NT3 asillustrated in FIG. 10B. The NMOS transistor NT2 has a gate electricallyconnected with the input node Nin, a drain electrically connected withthe power source node Nv, and a source electrically connected with anoutput node Nout and the source of the NMOS transistor NT3. The NMOStransistor NT3 has a gate and a drain electrically connected with thesource of the NMOS transistor NT2 and the output node Nout, and a sourceelectrically connected with the ground node Mg. Potentials supplied tothe nodes Win, Nv, and Kg the same as those in the case of FIG. 10A. Toreduce AC output impedance, a capacitor element nay be provided to theoutput node Nout as illustrated with dashed lines. With the sourcefollower circuit configured as illustrated in FIG. 10B, a constantpotential is output from the output node Nout.

Alternatively, as illustrated in FIG, 10C, the constant-potentialgeneration circuits 131 to 134 includes an NMOS transistor NT4 and anNMOS transistor NT5. The NMOS transistor NT4 has a gate electricallyconnected with the input node Nin, a drain electrically connected withthe power source node Nv, and the source electrically connected with anoutput node Nout and the source of the NMOS transistor NTS. The NMOStransistor NT5 has a gate electrically connected with a bias node Nb, adrain electrically connected with the source of the NMOS transistor NT4and the output node Nout, and a source electrically connected with theground node Ng. Potentials supplied to the nodes Nin, Nv, and Ng are thesame as those in the case of FIG. 10A. The bias node Nb may be suppliedwith, for example, a bias potential from a regulator circuit (notillustrated) in the chip regions 102 and 105. To reduce AC outputimpedance, a capacitor element may be provided to the output node Noutas illustrated with dashed lines. With the source follower circuitconfigured as illustrated in FIG. 10C, a constant potential is outputfrom the output node Nout.

In this manner, in the third modification of the embodiment, influenceof an external magnetic field on constant potentials supplied to thenodes N1 to N4 can be reduced to stabilize supply of the constantpotentials to the nodes N1 to N4.

Alternatively, as a fourth modification of the embodiment, acommunication system 1 r may have a configuration as illustrated in FIG.11. FIG. 11 is a diagram illustrating a circuit configuration and asignal transmitting operation of the communication system 1 r includinga magnetic coupling device 30 r according to the fourth modification ofthe embodiment.

The communication system 1 r illustrated in FIG. 11 includes themagnetic coupling device 30 r in place of the magnetic coupling device30 (refer to FIG. 1). The magnetic coupling device 30 r further includesinductors L3 to L4.

The inductor L1 is disposed between the coil 33 and the node N1. Theinductor L1 has one end electrically connected with the coils 33, andthe other end electrically connected with the node N1. The inductor L1is disposed with the central axis thereof aligned with the directionperpendicular to the surface of the substrate 2 (the Z directionillustrated in FIG. 2), and is wound in a direction opposite to adirection in which the coil 33 is wound.

The inductor L2 is disposed between the coil 34 and the node N2. Theinductor L2 has one end electrically connected with the coils 34, andthe other end electrically connected with the node N2. The inductor L2is disposed with the central axis thereof aligned with the directionperpendicular to the surface of the substrate 2 (the Z directionillustrated in FIG. 2), and is wound in a direction opposite to adirection in which the coil 34 is wound.

The inductor L3 is disposed between the coil 37 and the node N3. Theinductor L3 has one end electrically connected with the coils 37, andthe other end electrically connected with the node 133. The inductor L1is disposed with the central axis thereof aligned with the directionperpendicular to the surface of the substrate 5 (the Z directionillustrated in FIG. 2), and is wound in a direction opposite to adirection in which the coil 37 is wound.

The inductor L4 is disposed between the coil 38 and the node N4. Theinductor L4 has one end electrically connected with the coils 36, andthe other end electrically connected with the node N4. The inductor L4is disposed with the central axis thereof aligned with the directionperpendicular to the surface of the substrate 5 (the Z directionillustrated in FIG. 2), and is wound in a direction opposite to adirection in which the coil 38 is wound.

The operation for an external magnetic field is as illustrated in FIG.11. Specifically, when the external magnetic field H_(NOISE) is appliedas illustrated in FIG. 11, induced voltages of the coil 33 and theinductor L1 due to the external magnetic field H_(NOISE) are opposite toeach other as indicated by a dashed-line arrow. Accordingly, voltagechange occurring to the capacitor element C1 due to the externalmagnetic field H_(NOISE) can be reduced, and thus the noise currentsI_(NOISE) flowing to the differential driver circuit 41 can be reduced.

When the external magnetic field H_(NOISE) is applied as illustrated inFIG. 11, induced voltages of the coil 34 and the inductor L2 due to theexternal magnetic field H_(NOISE) are opposite to each other asindicated by a dashed-line arrow. Accordingly, voltage change occurringto the capacitor element C2 due to the external magnetic field H_(NOISE)can be reduced, and thus the noise currents I_(NOISE) flowing to thedifferential driver circuit 41 can be reduced.

When the external magnetic field H_(NOISE) is applied as illustrated inFIG. 11, induced voltages of the coil 37 and the inductor L3 due to theexternal magnetic field H_(NOISE) are opposite to each other asindicated by a dashed-line arrow. Accordingly, voltage change occurringto the capacitor element C3 due to the external magnetic field H_(NOISE)can be reduced, and thus the noise currents I_(NOISE) flowing to thedifferential receiver circuit 51 can be reduced.

When the external magnetic field H_(NOISE) is applied as illustrated inFIG. 11, induced voltages of the coil 38 and the inductor L4 due to theexternal magnetic field H_(NOISE) are opposite to each other asindicated by a dashed-line arrow. Accordingly, voltage change occurringto the capacitor element C4 due to the external magnetic field H_(NOISE)can be reduced, and thus the noise currents I_(NOISE) flowing to thedifferential receiver circuit 51 can be reduced.

In this manner, in the fourth modification of the embodiment, resistanceagainst the external magnetic field H_(NOISE) can be improved by usingthe inductors L1 to L4. The area of each inductor when viewed from abovemay be smaller than that of the corresponding coil, and the thickness ofeach insulating film may be reduced. Moreover, each inductor and thecorresponding coil may be stacked on each other in the Z direction. Withany of these configurations, the same effects as the above-describedeffects are acquired.

Note 1

A magnetic coupling device comprising:

a first coil;

a second coil electrically connected with one end of the first coil andwound in a direction opposite to a direction in which the first coil iswound;

a third coil facing the first coil;

a fourth coil facing the second coil;

a first constant-potential node electrically connected with one end ofthe third coil; and

a second constant-potential node electrically connected with one end ofthe fourth coil.

Note 2

The magnetic coupling device according to Note 1, further comprising:

a fifth coil electrically connected with the other end of the firstcoil;

a sixth coil electrically connected with the other end of the secondcoil and one end of the fifth coil and wound in a direction opposite toa direction in which the fifth coil is wound;

a seventh coil facing the fifth coil;

an eighth coil facing the sixth coil;

a third constant-potential node electrically connected with one end ofthe seventh coil; and

a fourth constant-potential node electrically connected with one end ofthe eighth coil.

Note 3

The magnetic coupling device according to Note 1,further comprising:

a first capacitor element electrically connected between a first circuitand the other end of the third coil; and

a second capacitor element electrically connected between the firstcircuit and the other end of the fourth coil.

Note 4

The magnetic coupling device according to Note 2, further comprising:

a first capacitor element electrically connected between a first circuitand the other end of the third coil;

a second capacitor element electrically connected between the firstcircuit and the other end of the fourth coil;

a third capacitor element electrically connected between a secondcircuit and the other end of the seventh coil; and

a fourth capacitor element electrically connected between the secondcircuit and the other end of the eighth coil.

Note 5

The magnetic coupling device according to Note 1 or 3, wherein the firstconstant-potential node and the second constant-potential node havepotentials different from each other.

Note 6

The magnetic coupling device according to Note 2 or 4, wherein

the first constant-potential node and the second constant-potential nodehave potentials different from each other, and

the third constant-potential node and the fourth constant-potential nodehave potentials different from each other.

Note 7

The magnetic coupling device according to Note 1 or 3, wherein the firstconstant-potential node and the second constant-potential node havepotentials equal to each other

Note 8

The magnetic coupling device according to Note 2 or 4, wherein

the first constant-potential node and the second constant-potential nodehave potentials equal to each other and

the third constant-potential node and the fourth constant-potential nodehave potentials equal to each other

Note 9

The magnetic coupling device according to Note 1 or 3, furthercomprising:

a first constant-potential generation circuit electrically connectedwith the first constant-potential node; and

a second constant-potential generation circuit electrically connectedwith the second constant-potential node, wherein

a reference potential of the first constant-potential generation circuitand a reference potential of the second constant-potential generationcircuit are common to each other.

Note 10

The magnetic coupling device according to Note 2 or 4, furthercomprising:

a first constant-potential generation circuit electrically connectedwith the first constant.-potential node;

a second constant-potential generation circuit electrically connectedwith the second constant-potential node,

a third constant-potential generation circuit electrically connectedwith the third constant-potential node; and

a fourth constant-potential generation circuit electrically connectedwith the fourth constant-potential node, wherein

a reference potential of the first constant-potential generation circuitand a reference potential of the second constant-potential generationcircuit are common to each other, and

a reference potential of the third constant-potential generation circuitand a reference potential of the fourth constant-potential generationcircuit are common to each other.

Note 11

The magnetic coupling device according to Note 1 or 3 furthercomprising:

a first inductor electrically connected between the one end of the thirdcoil and the first constant-potential node; and

a second inductor electrically connected between the one end of thefourth coil and the second constant-potential node.

Note 12

The magnetic coupling device according to Note 2 or 4 furthercomprising:

a first inductor electrically connected between the one end of the thirdcoil and the first constant-potential node;

a second inductor electrically connected between the one end of thefourth coil and the second constant-potential node;

a third inductor electrically connected between one end of the seventhcoil and the third constant-potential node; and

a fourth inductor electrically connected between one end of the eighthcoil and the fourth constant-potential node.

Note 13

The magnetic coupling device according to Note 3, wherein

the first circuit has a differential configuration, and

the third coil and the fourth coil are wound in directions identical toeach other.

Note 14

The magnetic coupling device according to Note 3, wherein

the first circuit has an in-phase configuration, and

the third coil and the fourth coil are wound in directions opposite toeach other.

Note 15

The magnetic coupling device according to Note 3, wherein

the first circuit has a single-phase configuration, and

the third coil and the fourth coil are wound in directions opposite toeach other.

Note 16

The magnetic coupling device according to Mote 4, wherein

the first circuit has a differential configuration,

the second circuit has a differential configuration,

the third coil and the fourth coil are wound in directions identical toeach other, and

the seventh coil arid the eighth coil are wound in directions identicalto each other.

Note 17

The magnetic coupling device according to Note 4, wherein

the first circuit has an in-phase configuration,

the second circuit has a differential configuration,

the third coil and the fourth coil are wound in directions opposite toeach other, and

the seventh coil and the eighth coil are wound in directions identicalto each other.

Note 18

The magnetic coupling device according to Note 4, wherein

the first circuit has a single-phase configuration,

the second circuit has a differential configuration,

the third coil and the fourth coil are wound in directions opposite toeach other, and

the seventh coil and the eighth coil are wound in directions identicalto each other.

Note 19

The magnetic coupling device according to Note 3, wherein the firstcircuit is a transmission circuit.

Note 20

A communication system comprising:

a transmission circuit;

a reception circuit; and

the magnetic coupling device according to any one of Notes 1 to 19disposed between the transmission circuit and the reception circuit.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit,the scope of the inventions. Indeed, the novel embodiments describedherein may be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

1-20. (canceled)
 21. A magnetic coupling device comprising: a first coilarranged substantially on a first plane. a second coil arrangedsubstantially on the first plane, the first coil being wound from a mostinner point to a most outer point along a first rotation direction whenseen from a vertical direction perpendicular to the first plane, thesecond coil being wound from a most outer point to a most inner pointalong a second rotation direction when seen from the vertical direction,the second rotation direction being opposite to the first rotationdirection; a third coil facing the first coil: a fourth coil facing thesecond coil; a first constant-potential node electrically connected withone end of the third coil; and a second constant-potential nodeelectrically connected with one end of the fourth coil.
 22. The magneticcoupling device according to claim 21, wherein the second coil iselectrically connected with the first coil at each most outer point, andthe third coil is separated from the fourth coil.
 23. The magneticcoupling device according to claim 21, wherein the third coil is toarranged substantially on a second plane, the second plane being apartfrom the first plane in the vertical direction, the fourth coil isarranged substantially on the second plane.
 24. The magnetic couplingdevice according to claim 22, wherein the third coil is arrangedsubstantially on a second plane, the second plane being apart from thefirst plane in the vertical direction; and the fourth coil is arrangedsubstantially on the second plane.
 25. The magnetic coupling deviceaccording to claim 21, further comprising a first capacitor elementelectrically connected with another end of the third coil; and a secondcapacitor element electrically connected with another end of the fourthcoil.
 26. The magnetic coupling device according to claim 22, whereinfurther comprising: a first capacitor element electrically connectedwith another end of the third coil; and a second capacitor elementelectrically connected with another end of the fourth coil.
 27. Themagnetic coupling device according to claim 21, wherein the third coilis wound from a most inner point to a most outer point along the firstrotation direction when seen from the vertical direction, and the fourthcoil is wound from a most inner point to a most outer point along thefirst rotation direction when seen from the vertical direction.
 28. Themagnetic coupling device according to claim 22, wherein the third coilis wound from a most inner point to a most outer point along the firstrotation direction when seen from the vertical direction, and the fourthcoil is wound from a most inner point to a most outer point along thefirst rotation direction when seen from the vertical direction.
 29. Themagnetic coupling device according to claim 21, wherein the third coilis wound from a most inner point to a most outer point along the firstrotation direction when seen from the vertical direction, and the fourthcoil is wound from a most inner point to a most outer point along thesecond rotation direction when seen from the vertical direction.
 30. Themagnetic coupling device according to claim 22, wherein the third coilis wound from a most inner point to a most outer point along the firstrotation direction when seen from the vertical direction, and the fourthcoil is wound from a most inner point to a most outer point along thesecond rotation direction when seen from the vertical direction.
 31. Themagnetic coupling device according to claim 21, wherein the third coilis separated from the fourth coil, the third coil is arranged on asecond plane and is wound from a most inner point to a most outer point,the second plane being apart from the first plane in the verticaldirection, the fourth coil is arranged on the second plane and is woundfrom a most inner point to a most outer point, the most outer point ofthe third coil is electrically connected to the first constant-potentialnode, and the most outer point of the fourth coil is electricallyconnected to the second constant-potential node.
 32. The magneticcoupling device according to claim 25, further comprising a pair of afirst input node and a second input node, wherein the first capacitorelement electrically connected between the first input node and thethird coil; and the second capacitor element electrically connectedbetween the second input node and the fourth coil.
 33. The magneticcoupling device according to claim 31, further comprising: a pair of afirst input node and a second input node. a first capacitor elementelectrically connected between the first input node and the most innerpoint of the third coil; and a second capacitor element electricallyconnected between the second input node and the most inner point of thefourth coil.
 34. The magnetic coupling device according to claim 25,further comprising a pair of a first output node and a second outputnode, wherein the first capacitor element is electrically connectedbetween the first output node and the third coil, and the secondcapacitor element is electrically connected between the second outputnode and the fourth coil.
 35. The magnet coupling device according toclaim 31, further comprising a pair of a first output node and a secondoutput node; a first capacitor element electrically connected betweenthe first output node and the most inner point of the third coil, and asecond capacitor element electrically connected between the secondoutput node and the most inner point of the fourth coil.
 36. Acommunication system comprising: a transmission circuit; and themagnetic coupling device according to claim
 21. 37. The communicationsystem according to claim 36, wherein the magnetic coupling devicecomprises a pair of a first input node and a second input node, and thetransmission circuit comprises a first output node electricallyconnected to the first input node of the magnetic coupling device andcomprises a second output node electrically connected to the secondinput node of the magnetic coupling device.
 38. The communication systemaccording to claim 36, wherein the magnetic coupling device comprises apair of a first input node and a second input node, and the transmissioncircuit comprises an output node electrically connected to both of thefirst input node of the magnetic coupling device and the second inputnode of the magnetic coupling device.
 39. A communication systemcomprising a reception circuit; and the magnetic coupling deviceaccording to claim
 21. 40. The communication system according to claim39, wherein the magnetic coupling device comprises a pair of a firstoutput node and a second output node, and the reception circuitcomprises a first input node electrically connected to the first outputnode of the magnetic coupling toes and comprises a second input nodeelectrically connected to the second output node of the magneticcoupling device.